<?php
/**
 * Slipstream :: Highly adaptive dependency injection framework
 * Copyright 2010-2011 Ian Unruh (Xerof3ar)
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
namespace Slipstream\Configuration\Context;

use ArrayIterator;
use Slipstream\Configuration\ContextInterface;

/**
 * Base implementation of WalkerInterface
 * 
 * @author Ian Unruh (Xerof3ar) <ianunruh@gmail.com>
 * @since Class avaliable since release 1.0
 */
class BaseWalker implements WalkerInterface
{
	/**
	 * @var ArrayIterator<ContextInterface>
	 */
	protected $currentIterator;
	
	/**
	 * @var ArrayIterator<ContextInterface>
	 */
	protected $pathIterator;
	
	/**
	 * @var ContextInterface
	 */
	protected $targetContext;
	
	/**
	 * Returns the current context the walker is on
	 * @return ContextInterface
	 */
	public function getContext()
	{
		if(is_null($this->currentIterator)) {
			return $this->pathIterator->current();
		}
		return $this->currentIterator->current();
	}
	
	/**
	 * Walks to the next context
	 * @return bool Returns true if there is a context to walk to
	 */
	public function next()
	{
		if(!is_null($this->currentIterator)) {
			$this->currentIterator->next();
			if($this->currentIterator->valid()) {
				return true;
			}
			$this->pathIterator->next();
		}
		return $this->initializeCurrentIterator();
	}
	
	/**
	 * Resets the walker to its initial position (the root context)
	 * @return void
	 */
	public function reset()
	{
		$this->currentIterator = null;
		$this->pathIterator->rewind();
	}
	
	/**
	 * Sets the target context to walk to
	 * 
	 * @param ContextInterface $targetContext
	 * @return void
	 */
	public function setTargetContext(ContextInterface $targetContext)
	{
		$this->targetContext = $targetContext;
		
		$path = array_reverse(iterator_to_array($targetContext, false));
		
		$this->pathIterator = new ArrayIterator($path);
		$this->currentIterator = null;
	}
	
	/**
	 * Creates an iterator for the current depth of the walker
	 * 
	 * @param ArrayObject<ContextInterface>
	 * @return Iterator<ContextInterface>
	 */
	protected function createCurrentIterator(ArrayObject $contexts)
	{
		return new ArrayIterator($contexts->getArrayCopy());
	}
	
	/**
	 * Initializes the current context's children iterator and returns true if
	 * the target context has not been reached
	 * @return bool
	 */
	protected function initializeCurrentIterator()
	{
		$currentContext = $this->pathIterator->current();
		if($currentContext == $this->targetContext) {
			return false;
		}
		$children = $currentContext->getChildren();
		$this->currentIterator = $this->createCurrentIterator($children);
		return true;
	}
}